How to turn "off" internal antenna while using External antennae?

I am beginning a project to put a home-made >18db  yagi on my CLEAR modem; in desiring to keep original functionality while adding ability for external attenna access, the installation of a PCB or case mount BNC suggests a need to turn "off" the internal antenna when the external is connected.
is this do-able?
if so, may I ask for assistance in understanding how please?
Thank you.

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You can always install a selector switch. Any 2 position SPDT switch will do. If your able to hack into where the internal antenna is at to break the traces and run them through the switch.
Ceyarrecks (author)  mpilchfamily4 years ago
additionally, here is a pic of the device disassembled; seems it has two separate antennae and a tiny ground plane.
Ceyarrecks (author)  mpilchfamily4 years ago
Thank you kindly; while yes, a physical break in the circuit would work, was thinking more on the electronic side,... or am I making this too complicated? :)
Adding a switch is on the "electronic" side. Any way you decide to go you will have to create a physical break in the circuit to disable the on board antenna. There is no way to go into the firmware and tell it to not use the on board antenna. There is no cutoff built into the board to handle that and it won't be able to tell you added an external antenna to the unit.

In the end you shouldn't have to disable any antenna. Solder the BNC leads in line with the existing antenna. As long as the wires to the BNC are properly shielded it won't add any interference. When you do plug an external antenna into the BNC connector your range will improve. The unit doesn't care where or how it gets the signal as long as it gets a good strong signal.
Ceyarrecks (author)  mpilchfamily4 years ago
that is a good point.
and considering the greater electrical signal from the external antenna should nullify any concerns I have about the physical switch.
I guess I was thinking of using ICs for the switch, which, yes, WAY more complicates this rather simple project.

Thank you for the input, it is most appreciated.

Re-design4 years ago
If the instructions tell you that it is better to turn off the antenna if an external antenna is used then there is probably a way to do this already built in to the unit. Post the model number etc. of the modem so we can look for information.
Ceyarrecks (author)  Re-design4 years ago
the type device I have is the CLEAR Hub w/ WiFi. It is not the one with an antenna jack.

Relays are a possibility, electronic switching probably not - it needs to switch in the microwave bands, and it needs to have a high loss in the off position. Special design techniques and knowledge needed.